The invention concerns an instrument for medical purposes, comprising a housing which can be introduced into an animal or human body, a movably mounted electromagnetic or acoustic transducer unit arranged in the housing, preferably in the distal end thereof, for producing electromagnetic or acoustic waves, in particular ultrasonic waves, and a drive for driving the transducer unit, wherein the transducer unit is connected to at least one first contact element and arranged on the housing is at least one second contact element provided for sliding contact with the first contact element.
Such instruments can be introduced into the human body or into cavities of the human body, which are accessible from the exterior, in particular for investigative purposes.
To carry out such an investigation of hollow organs and vessels, use is made in medicine inter alia of ultrasonic instruments, by means of which it is possible to obtain information about the structural makeup of biological tissue. By using sound waves, it is possible to observe structures within a piece of tissue, which are frequently only accessible to visual assessment by means of invasive methods. Within the human body however there are numerous cavities between organs and within bones which shield some regions of the body for the external use of ultrasound. Those regions can only be investigated by means of instruments of the kind set forth in the opening part of this specification, preferably ultrasonic instruments, which are to be introduced into the body. In that respect those instruments should be capable of processing sound waves at least in one plane in space so that a sectional representation of the body structure being investigated can be produced from the sound echoes which are received and evaluated by the instruments.
While there is sufficient space available for the scanning operation when using instruments outside the body, the tight conditions in respect of space in the body to be investigated constitute a problem when using instruments which are to be introduced into the body.
Dutch patent application No. 8700632 describes an ultrasonic instrument having a catheter whose tip either contains a rotatably mounted acoustic mirror or a fixed acoustic mirror and is itself mounted rotatably. A flexible shaft which is coupled to the rotatable mirror or the rotatable catheter tip extends from the distal catheter tip to the proximal end of the catheter and is driven by a drive unit disposed outside the catheter. A transducer is mounted in the catheter tip opposite the rotating acoustic mirror. Rotation of the acoustic mirror produces ultrasonic waves in different directions and the echoes of the sound waves are received again by the acoustic mirror and then by the transducer. As the curvature of the flexible shaft within the catheter is not in one plane, bending of the shaft in a plurality of axes relative to the position of the drive unit is also linked to a rotational movement of the transducer. As a result of this and due to static friction effects the directions of the ultrasonic waves cannot be accurately ascertained so that it is not possible to precisely predict how the image represented by the ultrasonic unit is linked to the position of the structure within the human body. The differing amount of friction which the flexible shaft experiences from one revolution to another also results in statistical modulation of the angular speed of the acoustic mirror, which reveals itself as a lack of definition in the image representation of the sound echoes.
To overcome those disadvantages, U.S. Pat. No. 5,603,327 to Eberle No. 5,603,327 proposes subdividing the fixedly installed ultrasonic converter into a plurality of segments, in respect of which the direction of propagation of the sound waves is achieved by suitable actuation control. That however gives rise to the necessity to provide numerous electrical contacting means in a very small space and in addition to integrate amplifiers for pre-amplification of the really weak echo signals from the numerous sound converter segments, into the instrument. That arrangement entails high manufacturing costs. If the instruments are used only once, which is frequently the case, that results in high consumable item costs on the part of the users.
A further possible option involves continuously measuring the position of the ultrasonic converter, whereby correction of the representation is a possibility. That measure is proposed in PCT publication WO 90/13253, assigned to DU-MED B.V. and published Nov. 15, 1990. For that purpose however it is necessary to use an angular measurement converter which however only permits correction of the visualized echoes, which is complicated and expensive in terms of computing power. Unfortunately complete elimination of the described friction effects is also not possible with such an instrument.
A third possible option involves moving the drive which moves the acoustic mirror or sound reflector into the catheter. Such an instrument is disclosed in European Patent Office application 0 423 895 A1, also owned by DU-MED B. V., which constitutes the most relevant state of the art which the present invention takes as its basic starting point. That known arrangement admittedly avoids the disadvantages of the previously described arrangements, but this arrangement only permits the acoustic wave radiation angle to be fixed in a narrow range. It has been found moreover that the structural factors involved with this arrangement means that it is essentially fixed only to high acoustic frequencies.
The object of the present invention is to improve an instrument of the kind set forth in the opening part of this specification, in such a way that it is possible to operate with the highest possible degree of versatility with a transducer unit which is flexible in particular in terms of frequency and radiation direction of the waves.
That object is attained in that, in an instrument of the kind set forth in the opening part of this specification, the first and second contact elements jointly form an at least radial mounting for the transducer unit.
Such an arrangement makes it possible to provide a transducer unit which is preferably rotatably mounted and which is substantially directly driven by the drive without the transducer unit requiring a large amount of space. In actual fact, the arrangement according to the invention in which the sliding contacts for contacting the transducer unit at the same time provide for radial mounting of the transducer unit and preferably also axial mounting affords a highly compact and at the same time reliable design configuration. A compact structure increases in particular the large number of possible uses of the instrument which in fact is also to be introduced into narrow natural or artificial openings in the body.
This arrangement also makes it easier for the drive and the transducer unit to be integrated in a compact housing. That affords various advantages. A major advantage is that on the one hand an acoustic mirror or sound reflector and on the other hand force-transmitting means such as for example a shaft are not required, which results in a simplified structure and a perceptible reduction in manufacturing costs. The damped elastic mounting for the transducer unit by the sliding contacts and the substantially direct rigid mechanical coupling of the drive and the transducer unit also reduces oscillations as a consequence of friction, which are superimposed on the movement which is predetermined by the drive, while in addition, by virtue of the very uniform movement of the transducer unit which is achieved in that way, that results in very uniform scanning by the waves generated by the transducer unit.
In addition there is a great deal of scope in regard to the design configuration of the transducer unit, in which respect in particular the frequency and the radiation angle can be virtually freely selected. Finally, the compact structure achieved by means of the arrangement according to the invention, which involves all necessary and mechanical components, permits simple assembly and dismantling, which results in inexpensive re-usability of essential components of the instrument.
Preferably the first and second contact elements also form an axial mounting. The axial mounting is preferably afforded by a peripheral groove in the first contact elements, into which engage contact springs of the second contact element. The engagement of the second contact elements into the respective peripheral grooves provides that the first contact elements are axially fixed with respect to the second contact elements without a rotary movement being impeded. In addition however it is also possible to provide other radial and possibly also axial mountings and/or seals which perform that mounting function.
The transducer unit can comprise one or more transducer segments, preferably acoustically operative segments.
A construction which is particularly preferred at the present time is distinguished in that the transducer unit is connected to at least one first contact element, at least one second contact element is arranged on the housing and the first and second contact elements are in mutual sliding contact, thereby affording continuous and reliable contacting and thus reliable electrical connection of the movably supported transducer unit. It will be appreciated that a plurality of first and second contact portions can be provided, in particular if the transducer unit comprises a plurality of transducer segments. In that respect the first and second contact elements each form a respective contact pair of which the second contact element forms the counterpart contact for the first contact element. Usually, at least two contact pairs are required for electrical contacting of the transducer unit so that the number of contact pairs is increased by at least one further contact pair for each segment which is to be freshly added if the transducer unit comprises more than one transducer segment.
The first and/or second contact elements are preferably elastically mounted, which ensures that the contact made is particularly certain. For that purpose it is also possible for the contact elements themselves to be of an elastic nature.
With such a contacting arrangement a plurality of contact elements which are elastically suspended independently of each other and which are electrically connected to each other can simultaneously contact one or more electrically interconnected contact partners which are rigidly connected to each other.
A development of this design configuration, which is particularly preferred at the present time, is distinguished in that the transducer unit is carried on a rotating and/or linearly oscillating shaft which is driven by the drive and on which the first contact elements are arranged. In that case the conductors connecting the first contact elements to the transducer unit can be arranged within the shaft, whereby the conductors are disposed in a particularly space-saving and compact fashion. For that purpose the shafts can be hollow and the conductors can be in the form of mutually insulated wires. For arranging the conductors within the shaft, it is either possible to select a coaxial structure or the conductors can be laid on the surface of an insulating layer applied to the inside surface of the shaft which is in the form of a hollow shaft. Equally the shaft itself can also be used as conductors, whereby it is possible to save on at least one wire, which also has an advantageous effect on manufacturing costs.
Desirably the second contact element is in the form of a spring, in which case the first contact element can be in the form of an annular portion surrounding the shaft and the second contact element can substantially tangentially touch the first contact element in order to achieve reliable contact. For that purpose the second contact element can be in the form of a straight or curved spring plate. Alternatively the second contact element can also be in the form of a coil spring surrounding the shaft, whereby it is possible to achieve a greater spring travel. In that case the cross-section of the movable second contact element can be adapted as desired to the demands of reliable contact-making. In particular square or round cross-sections of the individual contact springs, with a cross-section which is variable over the length thereof, are a possibility.
If the first contact elements are arranged on the shaft of the transducer unit and are contacted by the second contact elements by means of contact springs from the exterior, then the peripheral groove for implementing the axial mounting action is preferably disposed on the outside of the first contact elements.
Alternatively however spring contacts can also be provided on the transducer unit or the shaft thereof, being surrounded by contact sleeves with which they are in engagement. The contact sleeves are preferably arranged on the housing and for axial mounting thereof can have grooves on their internal peripheral surfaces.
The first and second contact elements can be arranged jointly in a first housing portion which is sealed off in relation to the rest of the housing and contains gas or liquid. This arrangement serves essentially for affording sealing integrity in relation to a medium which is used for acoustic coupling of the transducer unit which is in the form of an ultrasonic transducer. In this case neither the gas nor the liquid is to have an adverse effect in respect of the electrical properties, in particular electrical attenuation and insulation of different contact elements relative to each other, nor are the flow properties thereof to result in the contact elements floating up or in an inadmissible increase in the frictional moment.
For direct coupling to the transducer unit the drive should preferably be arranged in the housing, in the direct proximity of the transducer unit.
The drive can have an electrostatic, electromagnetic, piezoelectric, magnetostrictive or fluid motor and for the purposes of increasing torque can be selectively provided with a transmission which has one or more stages and which provides for a uniform or non-uniform step-up effect. It is additionally possible to provide a regulating means which for example can have an angle measurement converter, or a synchronous motor can be used for this purpose.
The transducer unit may optionally have a plurality of transducers, preferably ultrasonic converters, which are oriented axially and/or radially in relation to the longitudinal axis of the housing. In that case each of those transducers may in turn comprise one or more active segments of variable arrangement and shape. The contacting configuration when using a plurality of transducers and/or segments can in that case be such that current paths which are always at the same electrical potential can be combined together and contacted by way of a single contact element pair.
If the transducer unit has at least one ultrasonic converter it can be arranged in a second housing portion which is sealed off with respect to the rest of the housing and contains a fluid for acoustic coupling purposes.
Usually the instrument is provided with a catheter, with the housing being removably fixed to the distal end of the catheter. In that case therefore the housing forms a structural unit for receiving the drive, the contacting means and the transducer unit which can be assembled and dismantled in a simple manner in the form of a functional unit. This together with sterilizability of all components ensures economical re-usability.
Finally the housing can be in the form of a tube, particularly when it is fixed to a catheter.
Further preferred configurations of the invention are set forth in the appendant claims.